Update: This MINI54 is not recommended for new designs.
Use the MKL02/04 chip for new projects.

Inventory Status:

In Stock

Last physical count:

Aug 9, 2017

For developing projects, we highly recommend you use a Teensy board
to get your code working.

By using this Mini54 chip and a blank MK20DX128VLH5 or MK20DX256VLH7, you can build your own
Do-It-Yourself board that's compatible
with Teensyduino and Teensy Loader. Either chip will work. The MINI54 will automatically
detech which chip you've used and implement either Teensy 3.0 or Teensy 3.1.

These chips can also be very useful
for modest volume production of a fully custom product developed using
Teensy 3.0 or Teensy 3.1.

Crystal Guidelines

If an 18 pF rated crystal is used, two 20 pF capacitors should be added to
the design.

The crystal should be located close to the MK20 chip. A
ground plane should
be placed underneath the crystal. If using a 2 layer PCB design, the ground
plan for the crystal should NOT make any other connections to ground, other
than the crystal case ground, capacitor grounds (if adding extra capacitance)
and to the ground pin next to the crystal pins.

Never route any digital signal directly underneath the crystal (if disregarding
the ground plane advice). PCB designs that violate these rules have experienced
crashes or unreliable operation due to digital signals disrupting the crystal.

Avoid routing fast digital signals in parallel with either crystal trace. Normally
this is a non-issue, because ground is on one side of the crystal pins and RESET
is on the other side (RESET is safe, because it's held as a DC voltage while the
chip runs). Fast digital signals can capacitively couple to either crystal signal,
causing the oscillator stop or jitter, which can be particularly problematic if
the internal phase-locked-loop is using the crystal as its timing reference.

Poor crystal layout has caused several custom PCB designs to fail. Be careful
with the crystal layout!

Troubleshooting

Here are conversations from people who've used the MINI54 to build their
own boards. Many bits of troubleshooting advise and details are
available in these forum threads!

Pins shorted together obviously can cause trouble. If using a contract manufacturer
to assemble prototypes, make more than one board. Two or more for each comparison
can help reduce chances a random construction error ruins your otherwise perfect design.

Please understand the crystal start oscillating under software control. The
oscillator is NOT automatically enabled at power-up or reset. It is perfectly
normal for the crystal to not oscillate while the MK20 is held in reset state
or before software activates the oscillator. The MK20 always boots up to a
mode where it runs from an internal RC oscillator.

Thoughts on the business sense of making your own PCB
at different volumes and points within the product lifecycle, particularly before
establishing any sales trend or market demand. This technically isn't an issue
with the Mini54 chip, but it's perhaps the most common "problem" with custom boards.
Making your own PCB for learning or fun is always a good idea. Doing it for commercial
goals can be too, but isn't necessarily always a good path.